<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    .father {
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
      background: pink;
    }

    .son {
      background: red;
    }
  </style>
</head>

<body>
  <div class="father">
    <div class="son">子元素的内容</div>
  </div>
  <script></script>
</body>

</html>